With the production of electrical wire connections between a semiconductor chip and a system carrier, known in technical jargon as wire bonding, the fingers of the system carrier to be bonded are pressed against a heating plate by means of a holding plate. The holding plate has a window so that the ends of the fingers are accessible for bonding.
A Wire Bonder is a machine with which semiconductor chips are wired after mounting on a substrate. The Wire Bonder has a capillary that is clamped to the tip of a horn. The capillary serves to secure the wire to a connection point on the semiconductor chip and to a connection point on the substrate as well as to guide the wire between the two connection points. On producing the wire connection between the connection point on the semiconductor chip and the connection point on the substrate, the end of the wire protruding out of the capillary is first melted into a ball. Afterwards, the wire ball is secured to the connection point on the semiconductor chip by means of pressure and ultrasonics. In doing so, ultrasound is applied to the horn from an ultrasonic transducer. This process is called ball bonding. The wire is then pulled through to the required length, formed into a wire loop and bonded to the connection point on the substrate. This last part of the process is called wedge bonding. After securing the wire to the connection point on the substrate, the wire is tom off and the next bonding cycle can begin.
A downholder with which the holding plate has a movable bearing in order to achieve a uniform pressing of the fingers onto the supporting surface is known from the Swiss patent specification CH 680 176. This downholder does good service for system carriers with which the average distance between neighbouring fingers, known in technical jargon as the pitch, does not fall below a certain value. With a pitch of 50, 40 or only 25 micrometers however, considerable problems arise in particular because of the different thermal expansion coefficients of system carrier and holding or heating plate.
The object of the invention is to develop a downholder that is suitable for the processing of system carriers with an extremely small pitch of 40 micrometers or less.